Counterboring tool



Feb. 16, 1931. BERG 1,791,998

COUNTERBORI NG TOOL Filed Sept. 10. 1928 A/frea J. 56kg] Patented Feb. 10, 1931- ALFRED J. BERG, onaocKmenA new HAMPSHIRE counrnanoame moor.

Application filed September 10,1928. Serial No. 305,013.

My invention relates to back counterbormg and has for its object to provide a simple and effective means for holding the cutter for use in back counterboring onto the extension rod by which it is operated.

For the purpose of providing a suitable counterbore or countersink on the inside of armorplate for naval vessels to receive the head of a rivet it is often necessary, particularly in repairing armorplate in position, to introduce the extension rod or the tool from the outside and to fit onto the end of the extension, from the inside, the cutting tool required and to secure it on the extension so that by rotating this tool by a bit brace or other rotating means, the-cutting tool may be rotated to cut away the metal on the inside end 01" a rivet hole alreadybored, as on account of restricted space Within the armorplate it is difficult or impossible to rotate the counterboring or countersinking tool from the inside. In the counterboring or countersinking tools heretofore used for such work the cutter after being slipped onto the inner end of the extension rod has been held in place by a pin thrust through the cutter and into or through the extension rod. Under the conditions under which such tools are required to be used it is dificult to put the securing pin in place or to remove it and the pin is liable to he dropped causing delay to search for it or to obtain a new pin.

Mypresent invention has for its object to provide a retaining means for the cutters of back counterboring or countersinking tools which will be always in place, will be readily turned to position to permit the cutter to be placed in position on the extension rod and to the tool in position.

With the object above shown indicated and other objects hereinafter explained in view my invention consists in the construc tion and combination of elements hereinafter described and explained.

Referring to the drawings:

Figure 1 is a side view 01": a back counterboring or countersinking tool equipped w1th t1on.

tobe slipped onto it.

be then readily turned to position to retain the retaining device embodying my inven- I V Figure 2 isa side view of the end of the extension rodcf the tool showing the rotary device in POSltlOIl to permit the cutting tool 1 Figure (dis a view similar to Figure 2 but s owing the retainer turned to retaming position. s

Figure 4 is a detail view of the retainer and V i Figure 5' is an end view of the tool shown in Figure lshowing the retainer. in retaining position. V

In the drawings 1 indicates the shank of my back counter-bore adapted to be gripped-in a bit brace or ether means for rotating the tool. From this shank extends stem 2 which may be of any desired length. At its free end this stem is cut away to form the tool carrying portion '3 rectangular, or other than circular, in cross sec ion adapted to receive the countersink or counterhorecutter i. The end of the tool carrying portion is centrally bored at 5' and the bore is screwthreaded to receive the screw threaded portion 6 of a retainer for holding the cutter i. This retainer comprises the screw threaded portion 6 and the head 7 the head having the same shape in cross section as the tool carrying portion 3. The threads on the portion 6 and in the bore 5 are so cut that when the retainer is screwed to bring itagainst the end of the tool carrying portion 8 it will be in the position indicated in Figures 1, 8 and 5, that is, its sides will be out of line with the sides of the tool carrying portion 3, after 7 5 the cutter has been slipped over the retainer into operating position on the squared or otherwise non-circular portion 3, the retainer may, of course, be rotated in either direction to move its sides out of line with the sides of portion 3 so as to retain the cutter on the stem but the threads of the portion 6 of the retainer and the threads of the bore 5 are preferably so cut as to permit a slight rotation to. bring it to retaining position.

As-the retaining device need not be re moved from the end or the stem to move from position to let the cutter slip over it to retaining position or back to permit the cutter 10c to be slipped ofi it Will not be readily dropped or lost.

While this retaining device is particularly adapted and intended for use with the back counterboring or countersinking tools, I do not desire to be limited to its use With such tools as it is obviously adapted for holding any detachable cutter onto itsstem.

Having thus described my invention What I claim is In a boring tool ha-ving'one endof its stem adapted to be engaged by means for rotating the tool and having the other end of the stem made non-circular in cross sectionand having a screwthreaded bore extending into its end;

a cutter adapted to be fit onto such non-circular end of the stem and aretainer carried by the stem having its head conforming in cross section to the non-circular end of the stem and having a screwthreaded portion engaging the screwthreaded bore in the end of the stem.

In testimony whereof; I hereunto aifi-x my signature.

ALFRED J. BERG. 

